HttpWebRequest issue with MonoTouch

I have not been working with Monotouch (or the iphone for that matter) for too long, so I guess my problem is experience related.

I created an application that needs to communicate with a web service via json. I used the ported Json.NET library found here : https://github.com/chrisntr/Newtonsoft.Json

First I created a windows application using the Json.NET library, just to quickly try it out. It worked perfectly. Then I wrote the same exact code in MonoDevelop, and the server returns an error message that it cannot recognize the query at all. Note that I have checked if the serializer does its job properly - the json string is formatted correctly. Moreover, both applications behave in the same manner until getting the response from the server.

JsonSerializer serializer = new JsonSerializer();
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(the uri of the service);
request.Method = "post";
request.ContentType = "application/x-www-form-urlencoded";
Query login = new Query(); // the object that will be serialized
login.module = "auth";
login.data.Add("username", username goes here);
login.data.Add("password", password goes here);
using (Stream s = request.GetRequestStream())
 {
                using (StreamWriter w = new StreamWriter(s))
                {
                   StringWriter sWriter = new StringWriter(new StringBuilder());
                   serializer.Serialize(sWriter, login);
                  w.Write("&query="+sWriter.ToString());
                }
 }
using (HttpWebResponse resp = request.GetResponse() as HttpWebResponse)
        {
            var reader = new StreamReader(resp.GetResponseStream());
            JsonReader  r = new JsonTextReader(reader);
  Response login_response = (Response)serializer.Deserialize(reader, typeof(Response));
        }

When I first wrote the windows application, the server could not recognize my queries because the Content header was set to "application/json" and because it requires the query to be delivered as a key-value pair (with "开发者_开发知识库query" as the key). That is the reason for the w.Write("query = "+sWriter.ToString()); . In the php script that was provided as an example of calling the service, this line was setup like this: curl_setopt($ch, CURLOPT_POSTFIELDS, array('query'=>jsonEncode($data)));

However since I fixed the content type headers and added the "query=" in front of the string, the code works perfectly in Visual Studio and Mono Develop. It even ran on my android phone after I wrote it in Java. However, in MonoTouch, the server always fails to recognize the request stream as a query. What could be the cause of this? is there anything special that happens to the request stream in MonoTouch as opposed to everywhere else? Again, I have checked the string that gets into the stream, it is correct and the same for all the test applications.

Thank you in advance.

---

Reinstalled MonoDevelop and issue disappeared.